It becomes necessary in continuous production processes to be able to measure the temperature of the material being produced, for example wires, cables and filaments, and which due to the rapid movement involved, a contact type of measurement is not possible.
Where objects are at a temperature say in excess of 500.degree. C., non-contact temperature measurement of such objects is possible using present techniques which depend upon measurement of emitted radiant energy and thereby, knowing the surface emissivity characteristics of the material concerned, the temperature of a particular moving object can be calculated.
This method works quite well when the temperatures involved are in excess of say 500.degree. C., that is the figure specified above, but below this, for example in the temperature range 50.degree. C., the method becomes unreliable because of low values of emitted radiant energy, uncertainty concerning the emissivity characteristics of the material of the particular hot body being monitored, and the effects of background radiation on the eventual results obtained.